1. Field of the Invention
This invention relates generally to a driver circuit for a stepping motor having a rotation detection means, and in particular to for circuits driving a stepping motor, such as employed in a wrist watch, a clock and other portable devices.
2. Description of the Prior Art
FIG. 1 shows the construction of the stepping motor which is driven intermittently with low cost, small size and power dissipation, for example, the stepping motor for an analog electronic timepiece.
Such a stepping motor comprises a stator 1 made of a high permeability magnetic material, a coil 7 connected magnetically to the stator 1, and a rotor 6 made of a permanent magnet which is magnetized with more than two poles and connected magnetically to the stator 1.
The mechanical output of the rotor 6 is transferred to the gears 5, 4, 3 and 2.
The devices fixed to gears 5, 4, 3 and 2 are driven by the gears.
In such a stepping motor, the method of executing the low power dissipation attains a high efficiency of the electric-mechanical converter.
Another method of executing the low power dissipation is to provide a driver for a stepping motor which is driven with a low torque and at relatively low power at the normal time and which is driven by a higher torque and higher power when the rotor was not rotated due to a high load, etc.
The latter method is disclosed in U.S. Pat. Nos. 4,114,364 and 3,855,781. In the above driving method, the rotation detection means is important and in particular, it is undesirable in that the required space is increased, the mechanism is complicated and the power consumption is increased, in order to detect the rotation of the rotor.